October 18 – Winner By A Landslide

One of the amazing things about science is how often things at one scale apply at another as well. For example, you can measure the way that a cup of lye reacts with a cup of water and know how much heat will be produced if you use a ton of lye and a ton of water instead. Or you can simulate an earthquake using a piece of spaghetti and that will teach you something about how the San Andreas behaves. Or, as Peter and Mary are about to discover, you can use a pile of rice to discover why the Earth is round.


The images on the television were both frightening and fascinating. There had been a heavy rainfall in California and the runoff was rapidly eroding the base of a cliff, causing parts of the cliff to collapse in large chunks that splashed mud and mayhem when they fell. That would have been fascinating enough but on top of the cliff were several multi-million dollar mansions that were following the formerly stable cliff on its downward plunge.

“Wow!” said Peter as he watched a particularly large chunk of a swimming pool fall twenty stories into the surf below. “That was amazing!”

“Yes,” agreed Mary. “I’m glad that they got all of the people out. But what about their stuff?”

“I guess they’ve got insurance,” Peter replied. “But why did they build on the cliff?”

“Probably for the view. But what I want to know is why isn’t the cliff still still standing?” Mary puzzled. “It was doing OK before the rain, so why fall now?”

“I dunno. Who could we ask?” Peter wondered.

“Well, Mr. Medes is on vacation this week, so we can’t ask him,” Mary said. “And your mom is an astronomer, so she wouldn’t know. That just leave my dad. But he’s an engineer. He probably won’t know either.”

“Well, there’s only one way to find out,” Peter said. “Let’s go ask him!”

With that the two young scientists left the den where they had been watching television and sought out Mary’s father. Since it was Saturday, the first place they checked was the kitchen; in addition to being a popular engineering professor at the local university, he was also an amateur gourmet chef who liked to make special meals on weekends. Sure enough, he was in front of the stove, cooking raw rice in oil and fragrant spices.

“Oh, boy!” Mary exclaimed. “Costless Rican Rice again?”

“You betcha!” her father replied. “I wanted to use up the last of that roast chicken and we had enough vegetables to make this interesting. Peter, would you like to stay for dinner?”

“I’ll ask my mom,” Peter said as his belly rumbled in response to the smell of the cooking. Mary’s father laughed at the sound.

“It sounds as if your stomach has already decided the answer will be ‘yes'”, he said as he stirred the rice. “So what may I do to help you two? Or are you just drawn to the sight of a master turning leftovers into a meal fit for a king?”

“We had a question about cliffs,” Mary said. “Why do they fall down?”

“That is an excellent question!” Her father boomed in response. “And I’ll tell you the answer just as soon as I toss these odds and ends into the rice.”

With that, Mary’s father scrapped chunks of cooked chicken and vegetables that were left over from the previous week’s meals into the rice. Pouring in a carefully measured amount of water, he gave the mass a final stir and put a lid on top. He then turned the heat down and turned to his daughter and her friend.

“So you want to know why cliffs fall down,” he said. “Why do you ask?”

“Well, we saw these cliffs in California that were falling apart and dragging the houses that were on top of them into the mud,” Mary said. “But the cliffs were only about two hundred feet tall. We’ve got skyscrapers that are ten times as tall. So why do the skyscrapers stand up and the cliffs fall down?”

“It turns out that you have come to exactly the right person to answer that question,” her father replied. “Though Peter’s mother might have done just as well; this applies to her field as well.”

“It does?” Peter asked. “How?”

“You’ll see!” Mary’s father replied. “To start with, we’ll need a couple of plates, some toothpicks, and some uncooked rice.”

Mary quickly went to the pantry and grabbed the things that her father had listed off. Her father took the plates from her and placed on in front of each of the scientists. He then gave them each a toothpick and poured a cupful of rice onto each plate.

“In front of each of you is a pile of rice,” he said. “What I want you to do is to make the tallest cliff of rice that you can by scraping away the rice at the bottom of the pile with the toothpick. When you are done, what do you think the cliff will look like?”

“It will be just like a real cliff,” Peter confidently said. “It will go straight up.”

“I’m no so sure,” Mary countered. “I think it will be a lot slope-ier. It will probably lean over more.”

“Well, there’s only one way to find out,” her father said. “Start scraping!”

What do you think will happen? Try the experiment yourself!

The two started scraping at the base of their rice piles. But as soon as they would start to build up a small cliff, the bottom would slide out and a small cascade of rice would flow down, turning the vertical wall into a horizontal slope. After a few minutes of diligent scraping, Peter tossed down his toothpick in disgust.

“I give up!” he declared. “The rice won’t make a cliff! It is even worse than what we saw on TV!”

“Peter’s right,” Mary agreed. “You can’t make a tall cliff out of rice.”

“You are both right,” her father said. “You can’t make a tall cliff out of rice and you can’t make a skyscraper out of sand. And in both cases, the reason is the same.”

“It is?” Mary asked.

“Yes,” her father replied. “What is happening is that every stack of stuff is a balance of two things. There is gravity, which is pushing down on all the parts of it and there is cohesiveness which is trying to keep everything together. When gravity pushed on the center of a pile of rice or a cliff or a skyscraper, the force is straight down. That creates pressure on the grains of rice which gets bigger as you go deeper into the pile. The rice on top feels very little pressure while the rice at the bottom feels a lot. If the pressure on a grain of rice is about the same as the pressure on the grains around it, everything is stable and nothing moves. But if the pressure is lower on one side, then things naturally try to move in that direction. And when the difference in pressure is greater than the cohesiveness, then -“

“You get a landslide!” Mary exclaimed.

“That’s right!” her father agreed. “If you watched carefully during your experiment, then you probably saw that the rice-slides only happened on the side where you were scraping. That was because that was the only side where the pressure was changing.”

“Oh!” Peter said with a look of sudden understanding. “And that’s why the cliffs were falling. When the water eroded enough of the base, the pressure from the dirt piled up in the cliff was more than the strength of the stuff holding the cliff together and – pow! – we got a landslide!”

“That’s right. And that should also tell you why you can’t build a twenty story cliff of rice or a two hundred story cliff of sand,” Mary’s father said.

“Because rice isn’t as strong as sand and that’s not as strong as the steel in a skyscraper!” Mary said. “But why could Peter’s mother have told us this, too?”

“Because she works with planets,” her father replied. “And the one part of the definition of a planet that everyone agrees on is that they are round thanks to their own gravity.”

“I don’t get it,” Peter said.

“Imagine that you are building a cliff of sand,” Mary’s father said. “What happens if it gets too tall?”

“Some of it collapses,” Peter said.

“OK, now imagine that you’ve got a pile of sand as big as a planet,” Mary’s father said. “What happens to that cliff?”

“It will collapse,” Mary said.

“And if the cliffs that creates are too tall?”

“Then they will collapse too,” Peter said.

“And what happens if you keep doing that all around the planet-sized sand pile?” Mary father asked.

“I get it!” Mary said. “No matter where you look, the sand piles can only be so tall. And that means that everywhere you look, everything is about the same distance from the center of the planet. And that makes it -“

“Round!” Peter and Mary chorused together.

“That’s right,” Mary’s father said. “And now, if you two will clean up your budding planets and if Peter will call his mother, we can eat dinner.”

With that reminder, Peter’s stomach once more rumbled threateningly and all three laughed as they set the table for dinner.


October 17 – Live! On TV!

Today’s factismal: The first earthquake to be shown live on television happened in 1989.

It was a balmy October evening in San Francisco. The Giants were competing with the Oakland A’s for the pennant, and the two teams were warming up in preparation for game three. As the television sports casters searched for something to add a little local color to the broadcast, they were given the greatest exclusive in history: an earthquake struck the area. And not some piddly little 4.0; this was a 6.9 Mb earthquake! As the anchors tried to describe what was happening, the world saw buildings shake, highways fall, and homes crumble into rubble.

A section of the collapsed highway (Image courtesy USGS)

A section of the collapsed highway
(Image courtesy USGS)

Amazingly, there were only 63 people killed in the earthquake (the 1905 temblor was about 30 times stronger and killed 3,000 people). Most of these happened in Oakland where a double-decker highway collapsed on itself. Interestingly, many credit the baseball game for the low fatality count. Because many people had left work early in order to watch the game, the highways were relatively uncrowded which meant that fewer people were hurt.

California is almost certain to have another large earthquake in the next three decades (Image courtesy SCEC)

California is almost certain to have another large earthquake in the next three decades
(Image courtesy SCEC)

But what is even more amazing is that the danger isn’t over. There is a 99.7% chance that California will have another earthquake at least as powerful as this one in the next thirty years. So we know when the next big on will happen (soon); what we don’t know is where. And that’s where you can help. The USGS and Stanford University are developing a new type of distributed seismometer that uses the accelerometers in tablets, smartphones, and computers to provide more complete coverage of earthquakes; the data that this Quake Catcher Network gathers will then help them to narrow down when we can expect the next big one. If you’d like to take part, head over to:

October 16 – Almost Home

Today’s factismal: The closest known extrasolar planet is Alpha Centauri Bb, a mere 4.4 light years away!

There’s an old astronomy joke that goes “What is the name of the closest star?” Ask that of most people and they will say “Alpha Centauri”; of course they would be wrong (the correct answer is “Sol” or “our Sun”). But there is a newer joke that just became possible a year ago; it asks “What is the name of the closest Earth-like planet?” Though the correct answer is “Terra”, “Tellus”, “Dirt”, or “Earth” (they all mean the same thing), the best answer is “Alpha Centauri Bb”.

That’s because astronomers have discovered a planet just slightly larger than Earth (1.13 times our mass, 1.04 times our size) that is orbiting the second brightest star in the Alpha Centauri system. The three stars that make up Alpha Centauri are a bit strange; the two brightest (A and B) orbit each other at a distance ranging from that of Saturn to that of Pluto while the dimmest of the three (Proxima centauri) orbits the AB pair at what would be the distance of our Oort cloud (home of the comets). Using highly tuned spectroscopes, the astronomers were able to sort out a slight shift in the light from Alpha Centauri B that indicated a planet which they gave the designation of Alpha Centauri Bb.

An artist's deception of what the Alpha Centauri Bb system might look like (Image courtesy ESA)

An artist’s deception of what the Alpha Centauri Bb system might look like
(Image courtesy ESA)

Of course, there is some skepticism in the scientific community over whether or not Bb actually exists (hey, we’re scientists; skepticism is just what we do), especially given that no-one has observed Bb passing across the face of Alpha centauri B. However, that just means that we’re spending a lot more time watching that part of the skies right now. If you’d like to join in on the fun but don’t happen to have a 30 meter telescope in your backyard, then why not become a Planet Hunter? Using Keppler data, you’ll be able to discover planets of your very own!

October 15 – Smoking Hot

Today’s factismal: Thirteen years ago, the Galileo probe made the closest approach ever to Jupiter’s moon Io; it was just 112 miles away from the surface of the moon!

The four largest moons of Jupiter (Io, Europa, Ganymede, and Callisto) have a special place in the minds of all planetologists. They were the first new planets to be discovered in modern times (they were originally called planets; the astronomers only started calling them moons when there were too many to count on the astronomers’ fingers). They helped establish the validity of the Copernican model of the universe and destroy the Earth-centered one. And they helped to establish Galileo’s reputation as a scientist, which then helped change science from a descriptive endeavor to an experimental one.

Though the four Galilean moons are easily visible with a pair of binoculars, it wasn’t until Voyager 1 and 2 passed by that we got our first good look at them. And perhaps the most surprising of the four was Io. A small, rocky world, it was rapidly revealed to be the most volcanically active body in the Solar System. Covered by lava flows and sulfur frost, it was unlike any of the other moons we’ve seen. Obviously, it needed to be explored in more detail.

A close-up image of Io, taken by the Galileo probe (Image courtesy NASA)

A close-up image of Io, taken by the Galileo probe
(Image courtesy NASA)

And so we sent out another probe. Launched in 1989 and named Galileo for the discoverer of the four moons, its primary mission was to map Jupiter’s moons and to discover the secrets of Jupiter’s atmosphere using a secondary probe. And, from the time it arrived at Jupiter in 1995 until its final plunge into Jupiter’s atmosphere in 2003, it returned over 14,000 images of Jupiter and its moons that have forever changed the way that we see planetary formation.

If you’d like to learn more about the Galileo probe (or any other planetary probe), then why not join the Association of Lunar and Planetary Observers? They’ve got lots of information on every planet (even Earth), along with several citizen science projects that you can get involved with! http://alpo-astronomy.org/

October 14 – Acid Trip

Today’s factismal: Acid rain has about the same pH level as wine or beer.

In the late 1800s, the fogs of London were notorious not just for their thickness (“pea soup” being about the kindest appellation that they were given) but also for their effect. Going out in a London fog would leave you with a raspy voice, itchy eyes, and a dry, chapped skin. How could a little fog do so much damage? It was because at that time, London was powered almost exclusively by high-sulfur coal. When the sulfur from the coal combined with the water in the fog, it created a weak sulfuric acid solution (about as acidic as wine or beer); walking in the fog was literally like walking in acid!

How acid rain forms (Image courtesy EPA)

How acid rain forms
(Image courtesy EPA)

The fogs of London are now nothing but a memory, thanks to improved power generation methods, but acid rain is still with us. There are many places around the world (e.g., China, India) where it is cheaper and easier to burn high sulfur coal and oil to generate energy, which means that there is still plenty of sulfuric acid being formed. And, because the atmosphere doesn’t stop at a country’s borders, the pollution that one nation creates can easily affect other nations across the globe. However, quantifying that damage can be frustratingly difficult.

This fountain has been damaged by acid rain (My camera)

This fountain has been damaged by acid rain
(My camera)

And that’s where you come in. A group of scientists in Sydney (Utah) are looking for volunteers across the globe to go out and look at old gravestones in order to measure the effects of acid rain. The sulfuric acid created by sulfur pollution will slowly eat away at a marble gravestone; by measuring the amount of damage that’s been done, they can tell how much sulfur pollution the area has had. If you’d like to help, then head over to:

October 13 – Getting Old

Today’s factismal: This is the start of Earth Science Week – have you hugged a geologist today?

This week is Earth Science Week, celebrating all of the fun that can be found in studying the Earth. (Teachers: The AGI has a special free packet of goodies just for you!) So the posts this week will all be about earth sciences. And to start with, we’ll explore deep time.

The Earth is 4.6 billion years old (give or take a couple of weeks). But most people, heck most geologists, don’t have a good feel for just how long that really is. So I’ve taken the history of the Earth and put it into a time scale that we can appreciate: that of a 45-year old person. Looked at that way, the following events would have marked your life:

There – doesn’t that make you feel better about your mid-life crisis?

For more information on Earth Science Week, head over to the AGI website:

October 12 – Sparkling Water

Today’s factismal: Some dinoflagellates use bioluminescence to attract big fish that eat the little fish that eat dinoflagellates.

Obi-wan said it best: “There’s always a bigger fish”. And he probably learned that from dinoflagellates. These tiny little critters have a whip at one end that they use for propulsion, a shell made out of cellulose, and a variety of lifestyles that ranges the gamut from photosynthesis to hunter. Then again, with more than 2,200 species of dinoflagellate, there is plenty of room for just about any oddity. But perhaps the oddest thing that any dinoflagellate species does is flash blue lights when startled or jostled.

A dinoflagellate (Image courtesy David Patterson and Bob Andersen)

A dinoflagellate
(Image courtesy David Patterson and Bob Andersen)

Interestingly, it was that blue flash that first attracted people to them; the very first paper written about dinoflagellates was called “Animalcules which cause the Sparkling Light in Sea Water” and it hit the popular press way back in 1753. Today, quite a bit is known about how and why they flash. The reaction is similar to that of the firefly (and uses some of the same chemicals) but it happens for much different reasons. Like the firefly, they flash only at night. However, the firefly flashes in order to attract his lady-love and the dinoflagellate flashes to attract big fish (partly because dinoflagellates don’t have lady-loves. Poor dinoflagellate.). The rapid motion of small fish causes a pressure wave which triggers the flash; this is why they often flash in the wake of boats at sea. And the light that they generate attracts big fish that come to dine on the little fish that are feasting on the dinoflagellate.

A bioluminescent dinoflagellate (Image courtesy Maria Faust)

A bioluminescent dinoflagellate
(Image courtesy Maria Faust)

And the most interesting thing about the dinoflagellate flash is that it only happens within a specific pH range; if the water is too basic or too acidic, the poor dinoflagellate can’t flash. As a result, some ecologists in San Diego Bay are using the flash as a way of checking the water quality: flashing dinoflagellates means that everybody’s happy (except the big fish that thought it was a call to dinner). If you’d like to join the ecologists as they research more about dinoflagellates and the health of the bay, then head over to: